Double check valve device



cec/f mVENroR. ELLERY R. FITCH ArroRNEY.

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E. R. FITCH DOUBLE CHECK VALVE DEVICE Filed Aug. 2l, 1950 Il. um

Sept. 22, 1931.

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This invention relates to {iuid pressure brakes, and more particularly to a double check valve device ada ted to be employed in connection with a uid pressure brake equipment.

'It' has been proposed to employ the socalled automatic lapping brake valve device in a fluid pressure brake equipment. This type of brake valve device comprlses a spring adapted to be compressed so as to exert pressure on a movable abutment, by

the operation of the brake valve handle. When the spring exerts pressure on the abutment, the abutment is moved so as to unseat a fluid pressure supply valve and thereby effect the suppl of iuid under pressure to the brake cylin er. The pressure of Huid supplied the brake cylinder acts on the movable abutment in opposition to the spring pressure and when the brake cyhnder pressure has been increased to a degree slightly exceeding the pressure of the s ring, the abutment is operated to permit t e supply valve to close.

In a double end brake equipment, where a brake valve device is provided at each end of the car, when the operator leaves one end of the car to go to the other end, he removes the brake valve handle in handle olf position. This position is the brake application position, so that the brakes must be a plied when the operator leaves one end of t e car with the brake valve handle.

A double check valve device is interposed in the piping from the brake valve devices to the brake cylinder. The double check valve device is such that the pressure of fluidsupplied from the brake valve device at the non-operating end of the car holds the double check valve in position to establish communication from the operating brake valve to the brake cylinder.

When the operator leaves the operating end and removes the brake valve handle,

ingto the double check valve is vented to the atmosphere, permitting the ressure of fluid acting on the double chec valve as supplied from the end of the car which the o erator has just left, to shift the double c eck valve, so that communication is established at the new operating end of the 'car from the brake cylinder to the brake valve device. t 4

H brake valve -devices of the automatic lappng type are employed, there is liable to iferences in the pressure developed by dilerent automatic lapping brake valves, on account of manufacturing variations and the dilicul in adjusting both brake valve devices to evelop the same brake cylinder pressure.

As a result, if the non-operative brake valve device should develop a pressure sli htly below that of the operative brake va ve, then the higher pressure developed at the o erative brake valve may shift the double c eck valve, against the pressure developed on the double check valve by the non-operative brake valve so that communication will be established from the operative side of the double check valve to the non-operative side, with the result that fluid under pressure supplied to the double check valve from the brake valve device will How to the brake valve device at the non-operative end, and will be vented to the atmosphere by the operation of the brake valve device at the non-operative end.

The principal object of my invention is to provide a double check valve device of the above type, in which a differential pressure is automatically set up for preventing the movement of the double check valve from its intended operating positions, even though the pressure developed by one brake valve device be less than the pressure developed by theother brake valve device.

In the accompanying drawings; Fig. 1 is a diagrammatic view, partly in section, of a iuid pressure brake equipment including a double check valve device embodying my invention; Fig. 2 a section on the line 2--2 of Fig. 1; Flg. 3 a section on the line 3-3 of Fig. 1i and Fig. a section on the nected to pipe 22 of the left hand brake valve device and,l

, ed to enga line 4--4 Vof F1%1.

As shown in ig. 1, the equi ment is of the double end type having a rake valve device 1, at each end of the car, a main reservoir 2, a brake cylinder 3, and-a double check valve device 4.

Each brake valve device-1 comprises a casing in which is mounted a iston 5. A

coil spring 6 acts on one side o said piston` and carried at the upper end of said spring is a pressure plate 7, which is held against rotation by a pin 8, secured to a lug 9, and slidably engaging in a hole in the plate. The late 7 carries a pair of oppositely disose rollers 10 ada ted to engage the cam ace 11 of a rotatab e member 12. A hanglee 13 is operatively connected, to the memr 12. The movement of the piston 5 is adapted to operate a fluid pressure supply valve 14 `and a release valve 15.

-The double check valve device 4 comprises a casing having end cover plates 16 and 17 and containing a double check valve comprising pistons 18 and 19. The chamber 20 at the outer face of piston 8 is'con- 21, leading to the chamber the chamber 23 at the outer face oi the piston 19 is connected to a pipe 24 leading to the chamber 20 of the right hand brake valve device.

A seat ring 25 carried by piston 18 is adapted to engage an annular seat rib 26 when piston 18 1s moved to the right, and a seat ring 27, carried by piston 19 is adapta seat rib 28, when piston 19 is moved rom its outer to its inner position. f

The central chamber 29, formed intermediate the seat ribs 26 and 28 is connected by pipe 30 to the brake cylinder 3.

The piston heads 18 and 19 are connected together by a piston rod 31. Pivotally connected to the central portion of the rod .31 by a pin 32-are members 33,.each provided with a collar 34, on which a coil spring 35 seats. The outer -end portion of each member slidably extends through a hole provided in a rotatable pin 36, said pins being mounted in bearings provided in the check valve casing.

The springs 35 are under initial compression and when the pistons 18 and 19 are in the left hand position, as shown invFig. 1, the springs resist movement of the piston rod 31 and said pistons toward the ri ht. If the pistons are moved toward the right from the position shown in Fig. 1 until the members- 33 cross over the center line connecting the pins 36, then the angularity of the members 33 is changed, so that the springs then tend to move the pistons toward the right. The springs then operating to oppose movement of the pistons from the right hand position toward the left.

Assuming the parte positioned as shown in Fig. 1, with the operatin brake valve at the left, when it is desire to ap ly the brakes, the handle 13 is rotated, so t at the cam memberis rotated and the rollers 10 are depressed by the action of the cam face 11, to the extent correspondin with the de ree of rotation of the han e 13.

he spring 6 is thus compressed to a cor K chamber 22, and flows thence to pipe 21 and piston chamber 20 of the double check valve device. In the outer position of piston head 18, a roove 38 esta piston land communication being open to chamber 29, l'luid flows from piston chamber -20 to chamber 29 and thence to the brake cylinder 3.

When the pressure `of Huid supplied to chamber :22 and the brake cylinder has been vincreased to a degree slightly exceeding the pressure'of spring 6, the piston 5 will be moved upwardly, so as to permit the valve 14: to seat and cut oli' the further supply of Huid to the brake cylinder.

The handle having been removed from lishes communication from c amber 20 to the opposite side of the the non-(perating brake valve device at the right of ig. 1, with the parts in full service application position, the non-operating brake valve at the time of Vchanging ends, operated to supply Huid under pressure to the pipe 24 andthe pressure in chamber 23 is maintained to correspond with the compression of spring 6, and this pressure acts on the piston 19 and tends to hold same in its seated position. i

If the pressure developed by operation of the brake valve at the left should exceed the pressure developed by the brake valve at the right, the pistons will not be shifted to the right with my improvement, since the action of the springs 35 oppose the movement of the pistons toward the right. The differential pressure due to the springs, will overcome any possible difference in pressures d eveloped by the brake valve devices and willpthus prevent the unseating of the piston 19 by the pressure developed by operation of the brake valve device at the left of Fig. 1.

While one illustrative embodiment of the invention has been described in detail, it is not my intention to limit its scope -to that embodiment or otherwise than by the terms of the appended claims.

Having now described my invention, what I claimas new and desire to secure by Letters Patent, is

1.- A double check valve device comprising connected valve heads movable in one direction by iuid under pressureand movable in the opposite direction by fluid under pressure and a yielding resistance device for initially opposing movement of said valve heads in either direction of movement.

2. A double check valve device comprising valve pistons movable in one directlon by' iiuid under pressure supplied to one valve piston and movable in the opposite direction by fluid under pressure supplied to the other valve piston and a yielding resistance device having an angular position for opposing movement of said pistons in one direction and movable to another angular position for opposing movement of said pistons in the opposite direction.

' 3. .A double check valve device comprising valve pistons movable in one direction by fluid under pressure supplied to one valve piston and-movable in the opposite direction by uid under pressure supplied to the other valve piston and ,a spring operativelyconnected to said pistons and movable With said pistons to different angular positions on opposite sides of a neutral line,

to yieldingly oppose movementy of said pistons in one direction in one angular position and to yieldingly oppose movement-of said pistons in the `opposite direction in another angular position.

4. In a iuid pressure brake apparatus, the combination with a brake cylinder and two brake valve devices each operative to supply fiuid under pressure to the brake cylinder, of a'double check valve device compris- 40 ing connected valve pistons, operated by Huid under ressure supplied by either brake valve to positions for establishing communication from the other brake valve to the brake cylinder, and a yieldin resistance means for opposing movement o said double check valve from either of its positions.

5. In a Huid pressure brake apparatus, the combination with a brake cylinder and two' brake valve devices each operative to supply iuid under pressure to the brake cylinder, of a double check valve device comprising connected valve pistons, operated by fluid under pressure supplied by either brake valve to positions for establishing communication from the other brake valve to the brake cylinder, and a yielding resistance means having an angular position in which said means opposes movement of said double check valve from one position and movable 6o to another angular )position in which said means opposes movement of said double check valvefrom its other osition.

In hesimlfny lvrhlrof I f :fe hereuntooset my n',tis t a o ugust193.

EL'ERY R. FircH. 

